In a conventional pneumatic tire, when vertical load increases, a ground contacting area of the tread portion increases, and the cornering power of the tire increases. In other words, when the load on the tire decreases, the cornering power of the tire also decreases. Therefore, for example, on a front-engine and front-drive car having a large front load, the cornering power of a tire on a rear wheel is liable to decrease relatively more than the cornering power of a tire on a front wheel. Such an unbalance of the cornering powers causes a decrease of rear following capability while changing lanes and while cornering. Therefore, the improvement of the steering stability has been awaited.
Moreover, to improve the cornering power in all load range, for example, to enhance rubber hardness of the tread rubber is one idea, but there are possibilities to deteriorate driving noise and ride comfort. And, to decrease rigidity of a belt layer for tightening a carcass of the tire is another idea. However, there are possibilities of decrease in grip performance, driving noise performance, and antiwear performance.
The following Patent Document 1 discloses a pneumatic tire being capable of improving handle responsibility. However, in such a pneumatic tire, the circumferential rigidity of a central area of the tread portion having a ground pressure relatively large is set smaller than a shoulder region. There is therefore a problem that a deformation of the central area caused by a load change increases, and the cornering power cannot be improved in a low load range. Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-35130.